The present invention relates to a fuel cell system and, more particularly, to a fuel cell system and method which are able to prevent a reduction in power generation during starting of a fuel cell under low temperature conditions.
It has been known that scavenging is conducted by supplying a scavenging gas to a fuel cell while it stops power generation so that it can be not only restarted easily but also prevented from experiencing damage and degradation due to freezing of moisture, when it is used under cold conditions (below freezing point).
Japanese Published Patent Application JP2003-331893 discloses a method for supplying a scavenging gas bypassing a humidifier so that its humidity shifts to lower side. The reason for introducing this method is that when an oxidant gas or fuel gas is supplied to the fuel cell, the gas will be humidified by the humidifier provided in a gas passage.
However, this method has a drawback that when scavenging has been completed within the fuel cell, it has an adverse effect on power generation due to unevenness of humidity within electrodes. The unevenness is ascribed to the fact that the scavenging gas, which is a dry gas, tends to intensively dehumidify the vicinity of an inlet while it is flowing through the fuel cell.